For all you lift-serve skiers and boarders who brave I-70 to get your turns in:

SkiCarpool is a non-profit organization that facilitates carpooling to Colorado resorts through their website SkiCarpool.org

I used skicarpool.com a week ago and met a cool guy to ride with. We hit Winter Park and rode powder in the trees all day - it was fun. I like it, but you may have hit or miss experiences.